1. Field of the Invention
The present invention relates to a liquid crystal display (LCD). In particular, it relates to a LCD structure wherein gate and repair lines intersect only on one side of the gate line.
2. Description of the Related Art
Generally, a thin film transistor-liquid crystal display (TFT-LCD) has both a bottom and top glass plate. The TFT-LCD design typically arranges TFTs and pixel electrodes on the bottom glass plate. The top glass plate contains a common electrode and a color filter layer for displaying colors. Liquid crystal material fills the gap between the bottom and top glass plates. Additionally, polarizing layers, attached to the surfaces of both the bottom and top glass plates, polarize visible light rays.
LCDs with a TFT cell array formed on the bottom plate form poor panels if a defect opens or shorts any one of gate lines or data lines. Accordingly, to repair such a panel, a repair line is provided in the LCDs. The repair line is formed at the periphery of the TFT cell array region and connects to the shorted or opened data line or gate line allowing the TFT cell array to operate normally. When a defect is detected in or near one of the cells of the TFT-LCD cell array, the repair line replaces the defective gate or data line to repair the TFT-LCD. A conventional LCD repair technique is explained below with reference to the figures.
FIG. 1 shows a layout of a conventional LCD. FIG. 2 shows a cross-sectional view of portion I of FIG. 1. Referring to FIGS. 1 and 2, a substrate 11 contains a plurality of gate lines 1 arranged in parallel at a predetermined distance from one another. Gate lines 1 transmit drive signals to a plurality of pixels (not shown). Substrate 11 also contains a plurality of data lines 2 arranged in parallel at a predetermined distance from one another. Data lines 2 are perpendicular to the plurality of gate lines 1 and supply data signals to the plurality of pixels. A plurality of gate pads 1a and a plurality of data pads 2a are formed on adjacent sides of the TFT cell array and each connecting to a plurality of gate lines 1 and data lines 2, respectively. A repair line 4 intersects the plurality of gate lines 1 and data lines 2.
To determine whether the bottom glass plate of the LCD structure is defective, a drive signal and a data signal are supplied to gate pad 1a and data pad 2a, respectively. For example, if a data line is open at point 3, then a repair portion 5 of repair line 4 connects data line 2 and repair line 4. A laser (not shown) connects data line 2 and repair line 4, through insulating layer 12, where they intersect. Therefore, the TFT cell array can be driven even though it is connected to an opened data line.
FIG. 2 shows a cross-sectional view of portion I of FIG. 1. Conventional LCD structure for line repair includes a plurality of gate lines 1 formed in parallel at a predetermined distance from one another on a substrate 11 insulating layer 12 covers the surface of substrate 11 and the plurality of gate lines 1. Repair line 4 is provided and formed on insulating layer 12, and is covered by a passivation insulating layer 13.
The conventional LCD structure, however, has the following disadvantage. When one of the plurality of data lines 2 is opened and repair line 4 is used to transmit data signals, insulating layer 12 causes capacitance to formed between repair line 4 and one of the plurality of gate lines 1. The capacitance increases signal delay because signal delay is proportional to the product of capacitance and resistance, that is, T=R*C, wherein T is signal delay constant, C is capacitance, and R is resistance.
In light of the foregoing, there is a need for a line repair structure in an LCD that would reduce the time delay disadvantage of the conventional structure.